On the connective tissues and body cavities of the Nemerteaos. J^3 



inner circular muscle layer. In the posterior region of the body, 

 behind the rhynchocoelom, parenchym cells are found only around the 

 lateral vessels, and there only on those parts lying within the body 

 cavity (Fig. 2 Par). 



The parenchym cells (Figs. 12, 15) are polygonally spherical, often 

 of a more or less hexagonal form, caused by their mutual pressure. 

 The easily discernible, doubly refractive, non-staining cell membrane 

 is characteristic for this tissue, since the cells of all other connective 

 tissues are without membranes ; the membranes of adjacent cells are 

 in immediate contact, without the interposition of any intercellular 

 substance. The whole cell is filled with a structureless unstaining 

 fluid. The nucleus is spherical or oval, never elongated, and sur- 

 rounded by a small mass of finely alveolar cytoplasm, the latter 

 being placed excentrically against the wall of the cell ; from this cyto- 

 plasmic mass a few fine fibres radiate into the cell fluid, but, except 

 in the vicinity of the nucleus, it produces no layer on the inner 

 surface of the cell wall. 



In Carinella this tissue is more abundantly distributed than in 

 the other genera examined. 



4) The intracapsular connective tissue cells of the 

 central nervous system. (The term "intracapsular" was applied 

 by Bürger, '90, specifying its position within the brain capsule.) 

 These cells (Figs. 5, 10) are situated between inner and outer neuri- 

 lemma, and internally from the former (i. e. in and around the 

 fibrous core), in the brain and lateral nerve chords. These small 

 cells are multipolar, and their fine, branching fibres build a network 

 around the ganglion cells. Their nuclei are mostly oval, or some- 

 what elongated, and stain less deeply than those of the ganglion cells ; 

 the chromatin forms a network, as in Cerebratulus ] usually also a 

 spherical nucleolus may be found, which stains with eosin. Two 

 modifications of these cells occur in Carinella, though they are less 

 distinct than in Linens or Cerebratulus : 



a) Cells with a larger, more faintly staining nucleus; occurring 

 around the ganglion cells (Fig. 10). 



b) Cells with a smaller, but more deeply staining nucleus, which 

 is also more irregular in outline than in the preceding; occurring in 

 the fibrous core, within the inner neurilemma (Fig. 5). 



5) The interstitial connective tissue of the body 

 epithelium (discovered and described by Bürger, '90). This con- 

 sists of membraneless, multipolar cells (Fig. 8), whose branching. 



